The present invention relates to equipment utilized in subterranean well operations and, more particularly, to check valve assemblies operable to inject treatment fluids during stimulation operations while preventing inflow of production fluids.
In the course of drilling and construction of wellbores that traverse hydrocarbon bearing formations, it is oftentimes desirable to inject treatment fluids into the wellbore for a number of purposes. For example, hydrochloric acid solutions are often injected into the wellbore to stimulate the hydrocarbon bearing formation. In such cases, the hydrochloric acid solution can be injected into the subterranean formation to react with acid-soluble materials disposed in the formation, thereby enlarging pore spaces in the formation. These acidizing treatments are designed to improve the formation permeability, which consequently enhances production of reservoir fluids. Typically, such acidizing operations are performed at a high flowrate, but at a treatment pressure below the fracture pressure of the formation such that the acid is able to penetrate an extended distance into the formation without damaging the formation.
Attempts have been made to inject treatment fluids as reverse flow through conventional inflow control devices that utilize one or more flow restrictors such as flow tubes, nozzles, labyrinths, or the like. Inflow control devices are often used to control the rate of fluid inflow into a production casing and generally feature a dual-walled tubular housing with one or more inflow passages laterally disposed through the inner wall of the housing. A sand screen often surrounds a portion of the tubular housing, and production fluid can enter the sand screen and then negotiate, for example, a tortuous pathway between the dual walls to reach the inflow passages. The tortuous pathway serves to slow the rate of flow and maintain it in an even manner.
It has been found, however, that the flowrate required for acidizing operations is typically higher than the production flowrate from the formation. As such, reverse flow through conventional inflow control devices can result in an unacceptably high pressure drop in the treatment fluid. Accordingly, a need has arisen for an apparatus that is operable to enable injection of a treatment fluid into the wellbore and the surrounding formation. A need has also arisen for such an apparatus that is operable to enable injection of the treatment fluid at a high flowrate. Further, a need has also arisen for such an apparatus that is operable to enable injection of the treatment fluid without an unacceptably high pressure drop.